A solar battery generates electric energy from sunlight or artificial light of an incandescent lamp, a fluorescent lamp, or the like. The solar battery is constituted by a power generating layer made of a material such as amorphous silicon or an amorphous silicon alloy, or a power generating layer using microcrystalline silicon, crystalline silicon, a compound semiconductor material, or the like as the material thereof, and is conventionally mounted on portable electronic devices such as wristwatches, radios, electronic desk-top calculators, PDAs (Personal Digital Assistants) and the like. The portable electronic device with a solar battery mounted thereon is configured to be driven by electronic energy which is generated by conversion by the solar battery and accumulated in a secondary battery, and is increasingly demanded every year since it has an advantage that there is no need for replacement of a button battery and the like.
Since the portable electronic device with a solar battery mounted thereon is often carried in constant contact with a human body like a wristwatch, static electricity which is accumulated in the human body may enter and break the solar battery, resulting in remarkable degradation in characteristics of the solar battery (the breakage of the solar battery caused by the static electricity is referred to as “electrostatic-discharge damage”). This electrostatic-discharge damage is prone to occur when the solar battery is formed on an insulating substrate in particular, and thus a conventional portable electronic device with such a solar battery mounted thereon is given measures against the electrostatic-discharge damage in such a manner as shown in FIG. 16.
FIG. 16 is a cross-sectional view showing an internal structure of a conventional portable electronic device 101 with a solar battery mounted thereon. A solar battery 13 is provided with a bottom electrode 21 and an opposite electrode 23 on respective faces of a power generating layer 22, and the bottom electrode 21 is formed on an insulating substrate 12 to constitute a solar battery module 65. Further, the bottom electrode 21 and the opposite electrode 23 are connected to a drive circuit 31, and a shielding metal plate 15, which is an individual unit, is disposed in the vicinity of the solar battery 13 on the drive circuit 31 side and connected to a reference potential 32 (grounded). In the conventional portable electronic device 101, a route for dissipating static electricity entering from the outside as described above to the reference potential 32 (hereinafter, this route is referred to as a “dissipation route of static electricity”) is formed of the metal plate 15 to prevent the breakage of the solar battery 13.
However, since many portable electronic devices are downsized for convenience of carriage, they have accordingly great constraints on space for accommodating components and arrangement of them. Nevertheless, the conventional portable electronic device needs to separately secure a space for accommodating the metal plate 15, and thus there remains an extremely small margin of accommodating space of the components and arrangement of them, which presents a problem that flexibility in incorporating the components is remarkably low. In addition, the number of components increases by components associated with the metal plate 15, and the arrangement of the components needs to be separately devised for the parts associated with the metal plate 15, which presents a problem of increased cost.
The present invention is made to solve the above-described problems, and it is an object of the invention to provide a structure, in a solar battery module and a portable electronic device with the same mounted thereon, capable of avoiding electrostatic-discharge damage for higher reliability, and increasing flexibility in incorporating components for higher diversity, while having an advantage in cost.